Shrouded bit



United States Patent Office 3,416,618 Patented Dec. 17, 1968 3,416,618 SHROUDED BIT Elmer A. Kunnemann, Dallas, Tex., assigner to Dresser Industries, Inc., Dallas, Tex., a corporation of Delaware Filed Oct. 28, 1966, Ser. No. 590,435 3 Claims. (Cl. 175-339) ABSTRACT F THE DISCLOSURE A rotary drill bit for use in the drilling of oil and gas wells or the like with concentric drill pipe. The bit includes a body rotatably lsupporting a plurality of cutting members that are arranged on the body to disintegrate the bottom of the well bore as the bit is rotated. The body is arranged for connection with each of the concentric drill pipes. A shroud is attached to the body and forms a portion thereof. The shroud has an outside diameter substantially the same as the diameter of the well bore to prevent or at least inhibit fluid flow between the bit and the well bore wall. The shroud is extended downwardly as close to the well bore bottom as possible to increase the eiciency of recovery of the cuttings and to aid in preventing contamination of the cuttings.

This invention relates generally to an improved bit for use in drilling a well bore or the like. More particularly, but not by way of limitation, this invention relates to an improved bit for use with a pair of concentric hollow drill strings in the drilling o-f a well bore or the like.

Within the last few years, there has been developed in the oil industry a process for continuously obtaining samples of the formation in which the subterranean drilling operation is taking place. Generally, the continuous sam pling or coring process may be divided into two broad categories each of which utilizes concentric drilling strings extending from the surface of the well Ato the drill bit.

In the first category, the drill bit utilized is generally referred to in the oil industry as a core bit, that is, a bit capable of removing a substantially solid, `cylindrical core las the drilling proceeds. In this category, the core bit is attached to a combination bit sub and automatic core -breaker that provides for circulation of the air through the annular space between the concentric drill strings and for the separation of the cylindrical core into relatively short segments. The process utilized in this `category is clearly described in the Feb. 14, 1966 issue of the Oil & Gas Journal under the title of Rejuvenated Continuous Core Rig Takes the Field.

As clearly described in the foregoing article, drilling fluid, usually air, passes through the annular space and outwardly therefrom between the wall of the well bore and the outside of the core bit. The fluid then flows past the lower end of the bit upwardly into the interior of the inner drill string carrying the core therewith. While this process has proven generally satisfactory, there is some contamination of the core due to the engagement of the drilling uid with the wall of the well bore outside the drilling bit. Thus, the cuttings returned to the surface are ditcult to analyze.

In the second category, a very similar process is utilized except -that a rotating-cutter rock bit is utilized in lieu of the core bit. United States Patent No. 3,273,660 issued to J. G. Jackson et al. on Sept. 20, 1966 illustrates apparatus utilizing the aforesaid system in connection with the rotating-cutter rock bit. As clearly shown in FIGURE 1 of that patent, the rock bit has been modified to accommodate the concentric drilling string arrangement.

The diiculty encountered when attempting to use the modified rock bit in connection with the aforedscribed process is that there is no means provided to prevent contamination of the cuttings, that is, contamination of the core by well fluid or by material such as drilling muds which usually lls the well bore in .the annular space existing between the wall of the well bore and the exterior of the outside drill string. Thus, the crushed or fragmented core received at the surface is difficult to analyze due to its contamination.

This invention provides an improved bit for use in the aforedescribed process comprising: cutting means for forming the bore; a hollow body member operably supporting the cutting means and arranged to be connected with each of the drill strings, the body member having a shroud portion projecting from the body member and encircling a portion of the cutting means. The shroud portion has an outside diameter substantially equal to the outside diameter of the cutting means and substantially equal to the diameter of the well bore to contain the drilling fluid and to prevent contamination of the formation by mud or the like located in the annular space between the outer drill string and the wall of the well bore. A port in the body member provides communication ybetween the interior of the inner drill string and the well ybore adjacent the lcutting means. The bit also has at least one passageway extending through the body member within the shroud portion to provide communication between Ithe annular space and the well bore adjacent the cutting means. Thus, fluid in the annular space passes through the passageway within the shroud portion, engages the bottom of the well bore and -then flows through the port into the interior of the inner drill string. The shroud portion substantially prevents flow between the outside of the shroud portion and the well bore wall.

One object ofthe invention is to provide -an improved bit for use in the continuous coring process.

Another object of the invention is to provide an irnproved bit for use with concentric drill strings in the continuous coring process wherein contamination of the recovered core is substantially prevented.

A further object of the invention is to provide an improved bit for use in the continuous coring process wherein such process may be performed more eciently.

A further object of the invention is to provide an improved bit for use in the continuous coring process having a shroud portion thereon with an outside diameter substantially equal to the diameter of the well bore thereby preventing the contamination of the core `and promoting the eciency of the coring operation since the drilling fluids `are contained within the shroud and directed to engage the bottom of the well bore.

The foregoing and additional objects and advantages of the invention will become more apparent as the following detailed description is read in conjunction with the accompanying drawings wherein like reference characters denote like parts in all views and wherein:

FIGURE 1 is a vertical cross-sectional. view, par-tially schematic, illustrating a bit constructed in accordance with the invention disposed in a well bore during the performance of the continuous coring process;

FIGURE 2 is an enlarged, vertical cross-sectional view taken substantially along the line 2-2 of FIGURE 1 and illustrating in more detail the structure of the bit; and,

FIGURE 3 is a transverse cross-sectional View taken substantially along the line 3 3 of FIGURE 2.

Referring to the drawings land to FIGURE 1 in particular, shown therein and generally designated by the reference character 10 is a bit constructed in accordance with the invention. The bit 10 is disposed in a well bore 12 and is connected at its upper end 14 with an outer drill string 18.

A drill string 16 is disposed generally concentrically within the outer drill string 18 and is connected with the bit as will be described. The yconcentric drill strings 16 and 18 extend upwardly through the well bore 12 to a special drilling rig, only a portion of which is shown in FIGURE l. Manifestly, there is provided in -the drilling rig power-driven means (not shown) for rotating the concentric drill strings 16 and 18 to impart rotation -to the drill bit 10.

The inner drill string 16 is connected at its upper end in communication with a core recovery conduit 20. The conduit 20 serves to convey the recovered core or sample to appropriate apparatus (not shown) for separation of the core from the gas used in drilling so that the core can be analyzed.

The upper end of the outer drill 18 is connected to a swivel device 22 which is in turn connected to a cornpressor 24 by a conduit 26. The arrangement is such that compressed air from the compressor 24 passes through the conduit 26 and through the swivel 22 into an annular space 28 between the outside of the inner drill string 16 and inside ofthe outer drill string 18.

As illustrated in FIGURE 1, a casing 30 extends into the well bore 12. The upper end of `the casing is connected to a swivel 32 that permits relative rotation between the yconcentric drill string 16 and 18 and the casing 30. A conduit 34 connects the swivel 32 with a pump 36. The pump 36 is connected by Va pipe 38 with a reservoir 40 that is illed with drilling mud 42 or a similar substance utilized to load the annulus 44 existing between the outside of the outer drill string 18 and the wall of the well bore 12. A return conduit 46 extends from the swivel 32 to the reservoir 42 whereby the annulus 44 can be fully loaded.

Referring to FIGURE 2, it can be seen therein that the upper portion 14 of the bit 10 includes threads 48 connecting the bit 10 with the outer drill string 18. Also, it can be seen therein that the lower end' of the upper portion 14 of the bit is, that is, the medial portion of bit 10 is provided with threads 50 connecting the inner drill string 16 with the bit 10. An enlarged counterbore 52 extending downwardly from the threads 48 provides a continuation of the annular space 28 extending into the bit 10.

The bit 10 at its lower end 54 is provided with a plurality of downwardly extending arms 56. Each of the arms 56 is arranged to journal a cutter member 58. The cutters 58 are generally conical in configuration and include a plurality of rows of radially extending circumferentially spaced cutting projections 60. As is well known to those skilled in the well-drilling art, the cutters 58 rotate relative to the arms 56 as the bit 10 is rotated by the drill strings 16 and 18 forcing the cutting projections 60 into engagement with the formation and thereby forming the well bore 12.

A cylindrical shroud 62 encircles the lower end 54 of the bit 10 and is attached thereto in any suitable manner such as by welding as illustrated at 64. In order to maintain the outside diameter of the shroud 62 at a diameter substantially equal to the gauge diameter of the well bore 12 and of the cutting members 58, the shroud 62 includes notches 66 (see also FIGURE l) to provide clearance where the arms 56 approach the gauge diameter. Preferably, and as shown on the lower right portion of FIGURE 2 the shroud 62 extends downwardly as close to the bottom of the well bore 12 as is possible.

As shown in FIGURES 2 and 3, a plurality of passageways 68 are circumferentially spaced about the bit 10 outside of the inner drill string 16 and in communication with the counterbore 52. The passageways 68 extend downwardly through the bit 10 exiting between adjacent cutters 58 as is most clearly shown in FIGURES 3.

The bit 10 is also provided with a centrally-located port 70 that extends therethrough providing communication from the interior of the inner drill string 16 to the well bore 12 adjacent the cutters 58. It will be noted that all Cil the passageways 68 and the port 70 are within the connes of the shroud 62.

Operation To utilize the shrouded bit 10, it is connected by means of the threads 48 and 50 with the outer and iner drilling strings 18 and 16, respectively, and lowered into the well bore 12. When the cutters 58 engage the bottom of the well bore 12, the drill strings 16 and 18 and the interconnected bit 10 are rotated.

Simultaneously, air from the compressor 24 is pumped through the conduit 26, the swivel 22 and into the an-nular space 28 between the drill strings 16 and 18. Air passing downwardly through the annular space 28 enters the counterbore 52 in the bit 10 and passes through the passageways 68 exiting therefrom between the cutters 58 and engaging the bottom of the well bore 12.

As is well known, rotation of the cutters 58 in engagement with the bottom of well bore 12 ychips or pulverizes the formation being drilled. The air exiting from the passageways 68 serves to cool the cutters 58 to prevent their becoming overheated and also picks up the pulverized or chipped portions of the formation, that is, the core, carrying it upwardly through the port 70 into the interior of the inner drill string 16.

The cuttings or core passes upwardly through the interior of the inner drill string 16 through the swivel 22 and into the core recovery conduit 20. From the conduit 20, the cuttings pass through a device (not shown) wherein the cuttings are separated from the gasses and made ready for analysis.

From the foregoing description, it can be appreciated that the cuttings are returned from the bit 10 to the surface very quickly and are ready for an almost immediate analysis of the particular formation through which the drill bit 10 is passing. Thus, a geologist can ascertain almost immediately the exact formation in which the drill bit 10 is operating.

It should also be pointed out that since the outside diameter of the bit 10 and the shroud portion 62 are substantially equal to the gauge diameter, that is, the diameter of the well bore 12, well uid, such :as mud which is located in the annulus 44 for the purpose of controlling pressure and lubricating the drill string 16 and 18 is prevented from passing downwardly between the wall of the well bore 12 and the outside diameter bit 10. Thus, contamination of the samples returned from the formation being drilled is avoided.

Also, there will be no sidewall contamination since the air flowing downwardly through the passageway 68 is substantially contained within the shroud 62 and engages only the bottom of the well bore 12. Since the samples being returned are not contaminated either by fluids in the annulus 44 or by particles from the walls of the well bore 12, a very accurate analysis may be made on the samples and thus the precise formation in which the bit 10 is operated can be determined.

Manifestly, the bit 10 operates with a great deal of eiciency since the downwardly flowing air in the annular space 28 is not severely restricted, such las in prior art bits wherein the air passes out of the annular space and must ow between the wall of the bit and the wall of the well bore. Also, the downwardly owing air is directed onto the bottom of the well bore 12 wherein it most efciently aids in cooling the bit and carrying oi the cuttings formed thereby.

Having described but a single embodiment of the invention, it will be understood that it is presented by way of example only and that many changes and modifications can be made thereto without departing from the spirit of the invention or from the scope of the annexed claims.

I claim:

1. A rotary drill bit for use with a pair of concentric hollow drill strings having an annular space therebetween in the driling of a well bore or the like, said bit comprislng:

cutting means for forming the bore, said cutting means including a plurality of cutting members of generally conical configuration, each said cutting member having a plurality of rows of radially extending, circumferentially spaced cutting projections; and,

a hollow body member rotatably supporting said cutting means and arranged to be connected with each of said drill strings and said body member supporting said cutting members in spaced relationship to engage and disintegrate the bottom lot" the well bore upon rotation of said bit, said body member having shroud means projecting from said body member and encircling ra portion of said cutting means, at least a portion of said shroud means having a continuous, substantially circular exterior with an outside diameter substantially equal to the outside diameter of said cutting means and substantially equal to the diameter of the well bore,

a port in said body member providing communication between the interior of the inner drill string and the well bore adjacent said cutting means, and

at least one passageway extending through said body member and within said shroud means providing communication between the annular space and the well bore adjacent said cutting means, whereby fluid in the annular space passes through said passageway Within said shroud means engaging the bottom of the well bore and then through said port into the interior of the inner drill string, said shroud means substantially preventing iiow between the outside of said shroud means and well bore wall.

2. The bit of claim 1 wherein said body member includes a plurality of arm portions projecting therefrom a first end portion including a plurality of project ing arms, each said arm rotatably supporting 1 respective one of said cutting members,

a shroud portion projecting from said first en portion and encircling a portion of said arm and said cutting members, said shroud portioi having an outside diameter substantially equa to the outside diameter of said cutting membe; and equal to the diameter of said well bore,

a medial portion having an i-nternal thread foi connection with the inner drill string, a centrally located port providing communication betweer the interior of the inner drill string and the well bore adjacent said cutting members, and e plurality of circumferentially spaced passage ways ilocated between said arms and providing communication between the annular space and the well bore adjacent said cutting means and within said shroud portion, and

a second end portion having a threaded bore for References Cited UNITED STATES PATENTS substantially within said shroud means and Igea/ard a plurality of said passageways circumfere-ntially gr son 'T spaced about said port and between said arm 2261546 11/1941 Glpson UST-356 porticmg and 2,657,016 10/1953 Grable 175-215 one of said cutting members being rotatably sup- 2786652 3/1957 Wens 175-215 X ported on a free ensd of each said arm portion. 40 3151690 10/1964 Grable 175-215 X 3,273,660 9/1966 Jackson et al 175-215 X 3. A bit for use with a pair of concentric hollow drill strings having an annular space therebetween in the drilling of a well bore or the like, said bit comprising:

cutting means including a plurality of generally conically shaped cutting members for forming the bore; and

a hollow body member having CHARLES E. OCONNELL, Primary Examiner. R. E. FAVREAU, Assistant Examiner.

U.S. Cl. X.R. -213, 215 

